There is a case where, after a connection to a network is made through an access line, for which the authentication is required at the beginning of the utilization, and the user utilizes the services he or she desires through the network, the line is disconnected once because of some reasons, but the connection to the same line has to be made again. In such a case, typically, the authentication for the access line is carried out again to connect with the network. Specifically, one of following methods is adopted: (1) the user manually inputs the authentication information (i.e. a user ID and password) again to connect with the network; and (2) the authentication information is memorized in the terminal, and a communication program reads out this information at the time of the reconnection to connect with the network without any user's intervention.
However, in the aforementioned conventional technique, a processing for the authentication by the authentication apparatus or the like is required every reconnection. Therefore, large overheads are imposed on the authentication apparatus or the like. In addition, because it takes time to carry out the authentication processing, there is a problem that the user of the network cannot reconnect to the network soon. However, because the access line, for which the authentication is originally required, the authentication cannot be simply omitted.
Namely, the conventional technique cannot realize that the user terminal smoothly connects with the network while reducing the processing load for the authentication without deteriorating the security.